fix build error, add c# wrapper class

Tino Hager

2018-06-24 b2c03b1615535dc717e196c560901e9e420c96d6

 src/layer.c

@@ -11,6 +11,7 @@
#endif
      return;
   }
   if (l.mask)               free(l.mask);
   if (l.cweights)           free(l.cweights);
   if (l.indexes)            free(l.indexes);
   if (l.input_layers)       free(l.input_layers);